fyi, if you originally bought your phone from t-mobile and are now trying to swap over to a different network but it keeps saying "invalid sim card / sim card not supported" and you've exhausted every possible solution, tried literally everything to the point that even customer service is at a loss (restart, clear network data, replace potentially broken sim, airplane mode, etc) and when you ask they say your phone is definitely not network/carrier locked...
i want you to do me a favor: before you drive all the way out to a corporate store for assistance, before you spend hours upon hours on the phone with customer service...
i want you to go through your apps that you never use and look for one with a pink keyhole for an icon; it should be labeled something along the lines of "device unlock".
found it? good. now i want you to click it.
because, apparently, you need to manually unlock it yourself via this one inconspicuous app that you probably never even knew existed.
click "continue" and "permanent unlock" -- the request shouldn't take more than a few minutes to go through and then you'll have to restart your phone, but after that? you should be in the clear.
(all the googling i did and not one site ever mentioned this...)
(i'm still not quite sure why it didn't show up as network locked for customer service, though -- my best guess is that maybe it could only be done manually from the phone itself, thus customer service wouldn't see an option from their end for them to unlock it and so naturally assumed that must've meant that it was already unlocked...maybe? hm.)
